To manufacture semiconductors the industry uses various high purity gases. These gases are controlled by systems made up of high purity valves, regulators, pressure transducers, mass flow controllers and other components connected together by high purity metal seal fittings. These fittings may be undesirable because they add space between components and make it difficult to replace a component located between components. New modular surface mount manifold systems which overcome these problems have been recently introduced by several companies and are becoming very popular. Component manufacturers have reconfigured their components so the inlet and outlet ports and attachment mechanism are compatible with these manifolds. However, a simple economical check valve for these applications is needed.
Gas flow indicators of the general type under consideration are known in the art (See FIG. 1) and are shown and described for example in U.S. Pat. Nos. 2,963,563, 4,181,835, 4,313,111, and 4,763,114, the latter of which is hereby incorporated by reference. These prior art flow sensors generally comprise a device for use as a flow indicator to produce an electrical signal when flow through the device has reached a set range of flow rates. A cylindrical magnet is slidably mounted in a gas cylindrical passage for actuating a magnetic responsive switch. When the gas flow through the device reaches a predetermined range of flow rates, the pressure build-up causes the float to move against a gravity or spring bias. The movement of the magnet with the float actuates a reed switch or the like to produce an output signal indicating a predetermined flowrate has been reached.
These devices are generally contained in a housing which is not suitable for use in integrated gas systems used in semiconductor manufacturing which incorporate modular surface mount (MSM) technology. For an example of a system utilizing MSM technology see FIG. 2 and U.S. Pat. No. 5,605,179 to Strong. These integrated gas systems generally require a size reduction in the range of 50% to 60% in the axial direction, which makes it difficult to incorporate conventional fittings and the sensor in the significantly reduced space.
In addition, the semiconductor industry is increasingly demanding sensors and devices which are ultra-clean i.e., after manufacturing being capable of being cleaned to the highest standard of cleanliness in the industry. These prior art devices are generally welded together in several places which makes it extremely difficult and costly to clean and electro-polish the interior wetted surfaces after welding. Further, these devices require greater control to prevent misalignment during assembly between the float, the float guide and the body in order to provide consistent performance of the sensor.
Therefore, a new weld-free modular design of a flow sensor having improved alignment of the internal components and capable of being cleaned and electro-polished for use in a ultrapure semiconductor environment is desired. Further, a flow sensor is desired which is adapted to be received in a MSM system. It is further desired to provide a flow sensor which provides access to the reed switch without requiring the removal of the sensor from the system.
Still further it is desired to provide a check valve that is suitable for MSM applications.